1. Field of the Invention
The present invention relates to a network-based mobile communication technology.
2. Description of the Related Art
In mobile communication, to connect to a destination mobile terminal device, the area where the destination mobile terminal device exists always needs to be known (referred to as a “cell” in a mobile phone system and the like). Unexamined Japanese Patent Application KOKAI Publication No. 2006-108823 discloses a data communication system in which communication between mobile terminal devices (armature radio) is achieved by identifying the areas where the terminals exist.
In particular, recent years have seen an increase in the number of subscribers due to the dissemination of mobile communication. The area of coverage by each wireless station is made smaller for effective use of limited resources of wireless communication. As the area becomes smaller, the frequency of switching of area due to the travel of mobile terminal device users has increased, and location registration occurs frequently. The used portion of the wireless control channel increases, and location registration of mobile terminal devices becomes inefficient.
Unexamined Japanese Patent Application KOKAI Publication No. H9-191487 describes a mobile communication system for expediting location registration of mobile terminal devices so as to increase the success rate of registration. This mobile communication system comprises a plurality of base stations and a location register which registers the area where each mobile terminal device exists. Each base station services a plurality of mobile terminal devices, and the base stations are mutually connected via the network.
Each base station comprises a channel status detecting unit for detecting the status of channels and a channel assignment changing unit. Upon notification from a mobile terminal device that the wireless control channel is running out, the channel assignment changing unit temporarily changes a free channel to a channel for location registration based on the detection results of the channel status detecting unit.
A mobile terminal device comprises a channel monitoring unit and a location registering unit. Upon switching of area due to the travel of its user, the channel monitoring unit of the mobile terminal device notifies the base station that the wireless control channel does not have a space for location registration by the location register. The location registering unit performs location registration using a channel for location registration, whose role has been changed as specified by the base station.
When the portion of the used space increases in the wireless control channel, a free space of the general communication channel is temporarily used as a channel for location registration. The success rate of location registration requests increases, and base stations servicing terminal devices whose locations cannot be identified decreases. The quality of service improves accordingly.
The present invention is made in view of the foregoing problem. More specifically, the present invention is directed to providing a mobile communication technique that enables a data communication control apparatus, etc. to properly send data to a mobile terminal device that has already moved from one service area to another even prior to its location being registered in the location register.